The present invention relates to a buttonhole darning sewing machine for forming a buttonhole darning seam in a cloth while swinging a needle in tune with the feeding operation of the cloth, a buttonhole darning sewing machine for forming a buttonhole in a cloth using a cloth cutting knife, and a sewing apparatus including such buttonhole darning sewing machine.
In a buttonhole darning sewing machine for forming a buttonhole darning seam in a cloth while swinging a needle in tune with the feeding operation of the cloth and also for forming a buttonhole in a cloth using a cloth cutting knife, conventionally, as known well from Japanese Utility Model Publication No. 743305 of Heisei and the like, a cloth feed mechanism, a needle swing mechanism, a needle swing width change mechanism, and a base line change mechanism are respectively operated due to the rotation of a main cam which can be rotated in linking with the main shaft of the sewing machine.
And, recently, as known well from Unexamined Japanese Patent Application Publication No. 6-190164 of Heisei, there are provided a cloth feed motor, a needle swing width change motor, and a base line change motor, and, by driving or controlling these three motors, the cloth feed mechanism, needle swing width change mechanism, and base line change mechanism are respectively operated.
Also, referring to the cloth cutting knife, conventionally, as known well from Japanese Patent Publication No. 7-14438 of Heisei and the like, the cloth cutting knife is structured such that it is moved up and down once due to the rotation of the above-mentioned main cam.
And, conventionally, there are prepared cloth cutting knives respectively including cutting edges which correspond in length to buttonholes having different lengths; and, a cloth cutting knife corresponding to a given buttonhole is mounted on a knife mounting plate, and a buttonhole is formed in a cloth by moving up and down the cloth cutting knife once.
In forming a buttonhole using a cloth cutting knife in this manner, there are available a pre-sewing cutting processing or operation which is previously executed prior to formation of a buttonhole darning seam, and a post-sewing cutting processing which is executed after completion of formation of a buttonhole darning seam; and, there is also available a processing which is executed by moving down the cloth cutting knife just before completion of formation of a buttonhole darning seam.
In the case of the above-mentioned cloth cutting knife which is structured such that it is moved up and down once due to the rotation of the main cam, as described above, it is necessary to have prepared the cloth cutting knives which respectively include cutting edges corresponding in length to the different-length buttonholes. This not only raises a problem that the number of parts required is large but also requires a troublesome operation to mount a corresponding cloth cutting knife onto a knife mounting plate each time a buttonhole is changed.